(** Message output formatters.

    This module provides various output formats for validation messages,
    including text, JSON, and GNU-style formats for IDE integration. *)

(** {1 Formatters} *)

(** Format messages as human-readable text.

    Output format: [file:line:col: severity: message]

    @param system_id Optional default system identifier for messages without location. *)
val format_text : ?system_id:string -> Message.t list -> string

(** Format messages as JSON.

    Produces output compatible with the Nu HTML Validator JSON format.

    @param system_id Optional default system identifier for messages without location. *)
val format_json : ?system_id:string -> Message.t list -> string

(** Format messages in GNU style for IDE integration.

    Output format follows GNU conventions for error messages, compatible
    with most IDEs and editors.

    @param system_id Optional default system identifier for messages without location. *)
val format_gnu : ?system_id:string -> Message.t list -> string

(** {1 JSON Value Builders}

    These functions return [Jsont.json] values that can be reused
    for custom JSON encoding scenarios. *)

(** Convert a single message to JSON AST.

    Produces JSON compatible with the Nu HTML Validator format:
    {[
      {
        "type": "error",
        "message": "...",
        "subType": "error-code",
        "url": "...",
        "firstLine": 1,
        "firstColumn": 1,
        ...
      }
    ]}

    @param system_id Default system identifier for messages without location.system_id. *)
val message_to_json : ?system_id:string -> Message.t -> Jsont.json

(** Convert a message list to JSON AST with wrapper object.

    Produces JSON with a "messages" array:
    {[
      { "messages": [...] }
    ]}

    @param system_id Default system identifier for messages without location.system_id. *)
val messages_to_json : ?system_id:string -> Message.t list -> Jsont.json